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Abstract: SA-OR23

Continuous Non-Mutagenic DNA Damage in Podocytes Activates Pathogenic Memory T Cells Through Altered DNA Methylation

Session Information

Category: Glomerular Diseases

  • 1304 Glomerular Diseases: Podocyte Biology

Authors

  • Nakamichi, Ran, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka Naikagaku Kyoshitsu, Shinjuku-ku, Tokyo, Japan
  • Hayashi, Kaori, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka Naikagaku Kyoshitsu, Shinjuku-ku, Tokyo, Japan
  • Hishikawa, Akihito, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka Naikagaku Kyoshitsu, Shinjuku-ku, Tokyo, Japan
  • Itoh, Hiroshi, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka Naikagaku Kyoshitsu, Shinjuku-ku, Tokyo, Japan
Background

We have previously reported the association of KAT5-mediated DNA damage repair with altered DNA methylation in podocytes (Cell Rep 2019). Recent epigenome-wide studies suggested the association of altered DNA methylation in blood cells with kidney function. However, the mechanism and pathological significance has remained to be adequately elucidated.

Methods

To investigate the significance of DNA double-strand breaks (DSBs) in podocytes, we generated podocyte-specific I-PpoI-expressing mice. I-PpoI is a homing endonuclease which causes non-mutagenic DSBs.

Results

I-PpoI-mice developed nephrotic syndrome at 6 weeks of age and died because of renal failure around 24 weeks of age following rapid deterioration of renal function. Single-cell RNA seq analysis using renal cortex revealed a marked expansion of immune cells, especially CD8+ T cells exhibited a KLRG1low IL-7Rhigh memory precursor effector cell phenotype, with high expression of NKG2D receptors in I-PpoI-mice. The expression of murine NKG2D ligands, which are upregulated by DNA damage, increased in I-PpoI-mice podocytes. Upregulation of human NKG2D ligands in glomeruli was also observed in patients with various kidney diseases. NKG2D blocking prevented exacerbation of albuminuria and attenuated glomerulosclerosis and fibrosis in I-PpoI mice. Me-DIP seq analysis using peripheral blood cells revealed hypermethylated regions in I-PpoI mice, were enriched in binding sites for a transcription factor STAT1. I-PpoI-mice showed a significant increase in CD44high memory phenotype cells of peripheral CD8+ T cell populations, which was similar phenotype of STAT1 knockout mice. The chimeric WT mice with bone marrow (BM) cells of I-PpoI-mice exhibited an increase in albuminuria temporarily, whereas the chimeric I-PpoI-mice with BM cells of WT mice prevented renal fibrosis and renal death.

Conclusion

Continuous non-mutagenic DSBs in podocytes altered methylome of blood cells, including CD8+ T cells, leading sustained changes in immune microenvironment of the kidney and also BM. These results suggest the altered immune microenvironment in the kidney may be a therapeutic target preventing exacerbating glomerulosclerosis and renal fibrosis following podocyte DNA damage in CKD.